Due to growing environmental concerns, vegetable oils are finding their way into lubricants for industrial and transportation applications. The substitution of mineral oil with vegetable oil as a base stock for an environment friendly lubricant in a CI engine is explored in this study without adding any additives. The experiments have been conducted with a mixture of palm oil and mineral oil, at different compositions. Blends of palm oil and mineral oil in different compositions, 0, 25, and 50 (by vol %) were added to base SAE20W40 mineral oil to obtain different lubricant blends. The parameters evaluated include brake thermal efficiency, brake specific fuel consumption, volumetric efficiency, and mechanical efficiency and exhaust emissions. The engine performance and emission tests were carried out on a single cylinder, water cooled, 4-stroke CI engine. Compared to mineral oil, the palm oil-based lubricant revealed appreciable expedience on engine and emission performance.